Signature input apparatus and a signature verification system

ABSTRACT

The object is to improve the accuracy of signature input and signature verification and improve security by causing the handwriting of a signature to disappear by itself. The signature verification system includes a signature input apparatus 1 and a signature verifying apparatus 6. Signature input apparatus 1 has an externally charged type liquid crystal sheet 2 which has an underside being adhesive and is placed on a coordinate input unit 3. When a dedicated pen 5 having the function of applying static charge onto this liquid crystal sheet 2 is used to write a signature, the handwriting of the signature is liquid crystal representation on the display area of liquid crystal sheet 2 and this handwriting of the signature will disappear by itself after a predetermined period of time. Further, signature verifying apparatus 6 reads the handwriting coordinate information of a signature output from coordinate input unit 3 for detecting the handwriting coordinate information of a signature and verifies this handwriting coordinate information with the handwriting coordinate information of signatures which have been registered beforehand.

TECHNICAL FIELD

The present invention relates to a signature input apparatus and asignature verification system, and in particular relates to a signatureverification system comprising: a signature input apparatus whichdisplays the handwriting of a signature rendered by a coordinate pointeretc. as a liquid crystal representation and has a coordinate input unitfor detecting the coordinate information of the handwriting; and asignature verifying apparatus which reads the coordinate information ofthe handwriting and verifies it with the handwriting coordinateinformation of signatures which have been registered beforehand.

BACKGROUND ART

FIG. 18 is a block diagram showing a conventional signature verificationsystem. FIG. 19 is a block diagram showing the interior of a signatureinput apparatus constituting the signature verification system. Asunderstood from FIGS. 18 and 19, the conventional signature verificationsystem includes a signature input apparatus 100 and a signatureverifying apparatus 106, and signature input apparatus 100 and signatureverifying apparatus 106 are connected through a controller 103.

In signature input apparatus 100, a transparent, active type liquidcrystal display unit 101 is mounted on the top of a coordinate inputunit 102. This active type liquid crystal display unit 101 incorporatesa reduced thickness-type backlight 113 and a backlight power source 114.A signature which has been written on a display area 107 of active typeliquid crystal display unit 101 by a particular writer, using adedicated pen 105 is transferred to a coordinate input area 115 incoordinate input unit 102, where the handwriting of the signature isread out, specifically, the X-coordinate and Y-coordinate and itswriting pressure are detected by an X-axis driver circuit 116 and aY-axis driver circuit 117, a transmission/reception circuit 118 and aCPU 119.

As stated above, the handwriting coordinate information and writingpressure data detected by coordinate input unit 102 are transferred tosignature verifying apparatus 106 by way of controller 103, thentherein, are used for signature registration and signature verification.At the same time, the data is used for the calculation of thehandwriting coordinates in controller 103, the result being sent out toactive type liquid crystal display unit 101 as its display data. Basedon the transferred display data to liquid crystal display unit 101, thehandwriting of the signature is displayed on display area 107 viadisplay controller 111, memory 110, X-axis driver circuit 108 and Y-axisdriver circuit 109.

By repeating the above cycle of operations quickly, the handwriting ofthe signature is displayed as a liquid crystal representation on displayarea 107 as if it were being written on a paper surface by a writingimplement. Here, the active type liquid crystal display is one whichdisplays characters and/or patterns etc., by optically changing, byproviding an electric field or the like, the state of arbitrary dotsinside the display dots which are arrayed matrix-wise on a plane definedby the X-axis and Y-axis. Signature input apparatus 100 may incorporatea character generator 112 for character fonts for displaying typecharacters.

On the other hand, sent out from signature verifying apparatus 106 areinstructions such as the start of input of a signature (input start ofcoordinate input unit 102), transfer of the handwriting coordinate datato active type liquid crystal display unit 101, the end of input of asignature, and display deletion of active type liquid crystal displayunit 101. Since signature input apparatus 100 incorporates a voiceguidance unit 104 composed of an amplifier 121 and a speaker 120 forperforming voice guidance, the operation can be guided not only by theliquid crystal display but also by voice guidance.

However, active-type liquid crystal display unit 101 used in a signatureinput apparatus 100 of the conventional type, has the followingproblems, as compared to an externally charged type liquid crystal sheetfor displaying a signature as a liquid crystal representation byexternally applying a static charge.

A) The active type liquid crystal display unit uses a feedbackconfiguration of the coordinate position, needing additional arithmeticoperations, so that the response speed to the coordinate input is slowereven if the processing capacity is equal.

B) The active type liquid crystal display unit needs active elements forliquid crystal driving, and hence the liquid crystal-display itselfneeds a complicated structure and costs more.

C) The active type liquid crystal display unit tends to be thick, so itlacks flexibility.

D) The active type liquid crystal display unit uses a dotrepresentation, so the smoothness of the contours of the characters ofthe signature lowers.

E) When the active type liquid crystal display unit has broken down, itis very difficult to replace its liquid crystal display portion.

F) In the active type liquid crystal display unit, some adjustment isneeded so as to avoid the display coordinate positions deviating fromthe input coordinate positions.

G) In the active type liquid crystal display unit, the user cannot havea normal writing sensation such as when paper and a pencil are used.

H) The active type liquid crystal display unit needs a deletingoperation such as data rewrite etc., for canceling the handwriting of asignature after the liquid crystal display of the signature.

The present invention has been devised in order to solve the aboveconventional problems, and it is therefore an object of the invention toprovide a signature input apparatus and a signature verification systemincluding the same, wherein a liquid crystal representation of asignature can be performed by applying static charge, to allow thehandwriting coordinate information of the signature to be detected andthe characters of the signature to disappear by themselves.

DISCLOSURE OF INVENTION

A signature input apparatus of the invention comprises: a conductivelayer; a liquid crystal sheet at least having a liquid crystal dispersedpolymer layer in which a liquid crystal is dispersed in a polymermatrix; a coordinate pointer having the function of applying staticcharge onto the liquid crystal sheet; and a coordinate input unit fordetecting the handwriting coordinate information of a signature writtenusing the pointer, wherein the handwriting of the signature written onthe liquid crystal sheet disappears by itself. Therefore, there is noconcern that the handwriting will be viewed by others, thus improvingthe security.

Next, a signature verification system of the invention at leastcomprises:

(A) a signature input apparatus comprising: a conductive layer; a liquidcrystal sheet at least having a liquid crystal dispersed polymer layerin which a liquid crystal is dispersed in a polymer matrix; a coordinatepointer having the function of applying static charge onto the liquidcrystal sheet; and a coordinate input unit for detecting the handwritingcoordinate information of a signature written using the pointer, whereinthe handwriting of the signature written on the liquid crystal sheetdisappears by itself;

(B) a signature verifying apparatus which reads the handwritingcoordinate information of a signature output from the coordinate inputunit and verifies this handwriting coordinate information with thehandwriting coordinate information of signatures which have beenregistered beforehand. Since this configuration, in addition to theabove advantage, allows smooth handwriting to be displayed as a liquidcrystal representation on the liquid crystal sheet screen, it ispossible to easily write a signature and hence increase the precision,thus improving the accuracy of signature registration and signatureverification.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the first embodiment of a signatureverification system in accordance with the invention;

FIG. 2 is a block diagram showing the interior of the signature inputapparatus shown in FIG. 1:

FIG. 3 is a block diagram showing an embodiment of the signatureverification system shown in FIG. 1;

FIG. 4 is a schematic external perspective view showing the firstembodiment of a signature verification system in accordance with theinvention;

FIG. 5 is a schematic vertical sectional view showing the signatureinput apparatus shown in FIG. 1;

FIG. 6 is a conceptual diagram showing the coordinate detecting portionof the coordinate input unit shown in FIG. 5;

FIG. 7 is a schematic vertical sectional view showing the innerstructure of a dedicated pen used in the signature input apparatus ofthe first embodiment;

FIG. 8 is a block diagram showing the second embodiment of a signatureverification system in accordance with the invention;

FIG. 9 is a block diagram showing the interior of the signature inputapparatus shown in FIG. 8;

FIG. 10 is a schematic external perspective view showing the secondembodiment of a signature verification system in accordance with theinvention;

FIG. 11 is a block diagram showing the third embodiment of a signatureverification system in accordance with the invention;

FIG. 12 is a block diagram showing the interior of the signature inputapparatus shown in FIG. 11;

FIG. 13 is a schematic external perspective view showing the thirdembodiment of a signature verification system in accordance with theinvention;

FIG. 14 is a schematic vertical sectional view showing the signatureinput apparatus shown in FIG. 13;

FIG. 15 is a conceptual diagram showing the coordinate detecting portionof the coordinate input unit shown in FIG. 14;

FIG. 16 is a schematic vertical sectional view showing the innerstructure of a dedicated pen used in the signature input apparatus ofthe third embodiment;

FIG. 17 is a conceptual diagram showing the configuration of acoordinate input unit of a magnetostrictive plate type;

FIG. 18 is a block diagram showing a conventional signature verificationsystem; and

FIG. 19 is a block diagram showing the interior of the signature inputapparatus constituting the signature verification system shown in FIG.18.

BEST MODE FOR CARRYING OUT THE INVENTION

The liquid crystal sheet used in the present invention is composed of,mainly, a conductive layer, a liquid crystal dispersed polymer layer inwhich a liquid crystal is dispersed in a polymer matrix; and atransparent, surface protecting layer, all being laminated successivelyin this order.

The signature input apparatus in accordance with the invention has aconfiguration in which the liquid crystal sheet can be removablyattached to the surface of the coordinate input unit. This configurationallows the liquid crystal sheet of the invention to be removablyattached to a multi-purpose coordinate input unit. More specifically,the member constituting the side opposite the display screen of theliquid crystal sheet is preferably made up of an suction or adhesivematerial which allows itself to repeatedly be attracted to or be adheredto the surface of the coordinate input unit.

This conductive layer of the liquid crystal sheet may be of atransparent or opaque layer as long as it has a surface resistance of10⁷ Ω/cm or less. In practice, the conductive layer is composed of abase with its surface covered, so as to be conductive, with aluminum,titanium, chromium, tin, rhodium, gold, stainless steel, titaniumnitride, nickel-chromium, aluminum-chromium, or tin indium oxide. Thebase mentioned here is one which supports the conductive layer, andexamples include paper, cloth, felt, or plastic film such aspolyethylene terephthalate, polyethylene naphthalate, polypropylene,polyethylene, polyvinyl chloride, polysulfone, polyphenylene oxide,ionomer, polyimide, polycarbonate etc. Here, if the conductive layeritself is of a metal film, no base is needed.

The liquid crystal dispersed polymer layer of this liquid crystal sheetis one in which a liquid crystal is dispersed in a polymer matrix. Thetechniques for dispersing a liquid crystal in a polymer matrix include:a polymer-liquid crystal common solvent evaporation phase-separatingprocess (common solvent casting process); a polymerizationphase-separating process by which the polymer precursor in a liquidcrystal-polymer precursor mixture is caused by light or heat topolymerize; a fusing and cooling phase-separating process by which theliquid crystal and the polymer are cooled from the hot melted state; anda process of dispersing the liquid crystal in a polymer matrix byemulsifying and dispersing the liquid crystal into an aqueous resin andapplying and drying it; and the like. These techniques can be used asappropriate.

As for the polymer usable for this liquid crystal dispersed polymerlayer, a polymer which is hard to be mutually soluble with the liquidcrystal may be used. Specific examples include vinyl resin such aschlorinated polyethylene, polypropylene, polystyrene, acrylic resinetc., vinylidene chloride resin, polyvinyl acetal resin, celluloseresin, ionomer, polyamide, polycarbonate, polyphenylene oxide,polysulfone, fluororesin, silicone resin, styrene-butadiene rubber,chlorosulfonic polyethylene, polyester, epoxy resin etc. Here, polyvinylacetal resin includes polyvinyl formal, polyvinyl acetoacetal, polyvinylbutyral, etc.

As for the polymer constituting the liquid crystal dispersed polymerlayer, a polymer having a crosslinked structure (to be referred to ascross-linking polymer) is preferred. With a cross-linking polymer, thecross-linking polymer and the liquid crystal will never become mutuallysolved when the liquid crystal sheet of the invention is exposed to ahigh temperature state, so that it is possible to maintain a stableliquid crystal micro-dispersed structure. Accordingly, it is possible toproduce a liquid crystal sheet having durability, without anydegradation of performance with the passage of time.

Examples of the cross-linking polymer include: a cross-linking polymerobtained by mixing polymers having a functional group such as doublebond, hydroxyl, carboxyl, epoxy, isocyanate, amino etc., with across-linking agent which is reactive with the functional group; and across-linking polymer which is obtained by mixing a reactive polymerwith a polymer having a functional group of the above ones and causingreactions.

Examples of the cross-linking agent used in the above reaction,includes: di-isocyanate compounds, organic peroxides, amine compounds,epoxy compounds, dicarboxylic acid or carboxylic acid anhydride,formaldehyde, dialdehyde, diol, bisphenol, silanol compounds, metaloxides, metal halides, photo-cross-linking agent (photopolymerizationinitiator), etc. Examples of reactive polymers include phenol resin,amino resin, polyisocyanate, polyol, epoxy resin etc.

Preferable cross-linking polymers are ones which is obtained by reactingdi- or polyisocyanate with a polymer such as polyvinyl acetal resin,epoxy resin, acrylic resin, polyester resin etc. More preferablecross-linking polymers are ones which is obtained by reacting di- orpolyisocyanate with polyvinyl acetal resin. Here, examples of polyvinylacetal resin include polyvinyl formal, polyvinyl acetoacetal, polyvinylbutyral etc.

As for the liquid crystal used for the liquid crystal dispersed polymerlayer, it is preferred to use a nematic liquid crystal having a positiveanisotropic dielectric constant, being in its liquid crystal phase inthe temperature range from -10° C. to 100° C., from the technical standpoint, and having a differential index of birefringence (Δn) of 0.2 ormore in order to produce a clear display of a recorded image.

The volume resistivity of the liquid crystal dispersed polymer layer ofthe liquid crystal sheet, from the standpoint of the self-disappearingperformance of the handwriting of a signature written on the liquidcrystal sheet, is preferably equal to or greater than 10¹³ Ω.cm andlower than 10¹⁶ Ω.cm at a temperature of 20° C. at a relative humidityof 90%. With these settings, when the coordinate pointer is used toapply static charge to the liquid crystal sheet, the liquid crystalinside the liquid crystal dispersed polymer layer, at which writing isbeing written, is aligned by the electric field, so that the handwritingcan be recognized. At the same time, the static charge applied to thehandwriting portion moves at the top and bottom of the liquid crystaldispersed polymer layer with the passage of time and is neutralized, sothat the handwriting will disappear by itself after a predeterminedperiod of time. Accordingly, the problem of security can be eliminated.

In the signature input apparatus and signature verification system ofthe invention, when the liquid crystal sheet is composed mainly of aconductive layer, a liquid crystal dispersed polymer layer in which aliquid crystal is dispersed in a polymer matrix, and a transparent,surface protecting layer, all being laminated successively in thisorder, the liquid crystal dispersed polymer layer needs to have a volumeresistivity of 10¹³ Ω.cm or higher and lower than 10¹⁶ Ω.cm at atemperature of 20° C. at a relative humidity of 90%, and the surfaceprotecting layer needs to have a volume resistivity of 10⁹ Ω.cm orhigher and lower than 10¹⁶ Ω.cm at a temperature of 20° C. at a relativehumidity of 90%. Specific examples of the transparent, surfaceprotecting layer of the liquid crystal sheet include: vinyl resin suchas chlorinated polyethylene, polypropylene, polystyrene, acrylic resinetc., vinylidene chloride resin, polyvinyl acetal resin, celluloseresin, ionomer, polyamide, polycarbonate, polyphenylene oxide,polysulfone, fluororesin, silicone resin, styrene-butadiene rubber,chlorosulfonic polyethylene, polyester, epoxy resin, and mixtures ofthese, etc. The surface protecting layer may be obtained by laminating afilm made up of the above material, using a sticky material or adhesive,by applying or spraying the material and drying it, or by applying areactive material solution and causing the reaction after application.The surface protecting layer may be added with additives such as asurfactant, conductive micro-particles, UV absorbent, light stabilizer,etc.

Examples of the coordinate input unit used in the signature inputapparatus of the invention, include: one which detects the X-axis andY-axis coordinate data of the handwriting of a signature which iswritten by a coordinate pointer having the function of applying staticcharge to, or erasing static charge from, the liquid crystal sheetwithin the coordinate input area; or one which not only detects thecoordinate data of the handwriting, but also detects writing pressure,and further detects, the X-axis and Y-axis coordinate data when thecoordinate point is floating within a certain height in the coordinateinput area. Specific examples of the coordinate input unit include: anelectromagnetic induction type, pressure-sensitive resistance type,pressure-sensitive contact type, magnetostrictive type, capacitancecoupling type, magnetic coupling type, etc.

In the signature verifying apparatus used in the signature verificationsystem of the invention, the X-axis and Y-axis coordinate data(including that when the pen was floating) and the writing pressure datadetected by the coordinate input unit during the input of a signature bya dedicated coordinate pointer, are transferred to be used for signatureregistration and signature verification. Further, the signatureverifying apparatus is able to instruct the start of input of asignature, the end of input of a signature, and re-input etc., as wellas presenting the verification result etc., through voice guidance. Itis also possible for the signature verifying apparatus to have thefunction of inputting an ID card or ID number in addition to thesignature verification.

The signature verification system of the invention may be configured asan independent system which, for example, controls admittance to a roomby verifying the signature. In this case, the signature verifyingapparatus uses a computer which has verification software and memoriesfor registration data installed therein. The signature verificationsystem of the invention, can be connected to a variety of networks via adedicated or multi-purpose communications line. In this case,communication software is also installed to the above-exemplifiedcomputer. However, if the verification software and/or the memories forregistration data are built in any other unit or a dedicated unit, thiscomputer does not need to have the above software and/or memory. Thesignature verification system of the invention, can be constructed sothat it can be used both ways, as the above independent system and asthe configuration which is connected to various networks.

Next, the embodied modes of the signature input apparatus and signatureverification system in accordance with the invention will be describedin detail with reference to the drawings.

The First Embodiment

FIG. 1 is a block diagram showing the first embodiment of a signatureverification system in accordance with the invention. FIG. 2 is a blockdiagram showing the interior of the signature input apparatus shown inFIG. 1. FIG. 3 is a block diagram showing an embodiment of the signatureverification system shown in FIG. 1.

As shown in FIGS. 1 and 2, signature input apparatus 1 includes acoordinate input unit 3 and an externally charged type liquid crystalsheet 2 placed thereon with its underside being adhesive. A signatureverifying apparatus 6 is directly connected to coordinate input unit 3of signature input apparatus 1, while liquid crystal sheet 2 isseparated independently. Signature input apparatus 1 also has a voiceguidance unit 4 for instructing the start of input of a signature, theend of input of the signature and re-input etc., which are all sent fromsignature verifying apparatus 6 and presenting the verification resultetc., through voice guidance. Voice guidance unit 4 is composed of anamplifier 12 and speaker 13.

Coordinate input unit 3 in FIG. 2 is of a pressure-sensitive resistancetype, in which a dedicated coordinate pointer (to be referred tohereinbelow as a dedicated pen and its inner structure will be describedlater) 5 having the function of applying static charge onto liquidcrystal sheet 2 within a coordinate input area 8 of this coordinateinput unit 3 is used to write a signature, from which handwriting willbe detected on the X-axis and Y-axis coordinate data and writingpressure data, by an X-axis driver circuit 9, Y-axis driver circuit 10and CPU 11. The X-axis and Y-axis coordinate data and writing pressuredata of the handwriting of the signature thus detected by coordinateinput unit 3 are transferred to signature verifying apparatus 6, wherethey are used for signature registration and signature verification.

On the other hand, instructions of the start of input of a signature,the end of input of the signature, and re-input etc. as well as theverification result etc. are informed of from signature verifyingapparatus 6 by voice guidance unit 4. The handwriting of a signaturewritten by dedicated pen 5 onto a display area 7 of liquid crystal sheet2 is displayed as a liquid crystal representation, simultaneously withthe input of the signature, and this handwriting of the signature willdisappear by itself after a certain period of time. This configurationprovides for improvement of security, without allowing a third person toview the handwriting of the signature. Further, liquid crystal sheet 2is able to perform liquid crystal display of a varying width ofhandwriting, by making use of the tip of dedicated pen 5 elasticallydeforming in accordance with writing pressure.

Signature verification unit 6 used in this embodiment, as shown in FIG.3, is a computer 14 having communications software, verificationsoftware, and memories for registration, installed therein. Thiscomputer 14 is configured so as to implement ID input 15 of ID cards, IDnumbers etc. in addition to signature verification. Further, computer 14is connected to a variety of networks 16 via communications lines,either, dedicated ones or multipurpose ones. Further, based on theresult of the signature verification, a door unlocking operation 17 canbe performed. A switching mechanism (not shown) is provided for computer14, which determines whether the signature verification system of thisembodiment is used as an isolated system for performing only doorunlocking operation 17, or is only used for connection to network 16, oris used for both.

FIG. 4 is a schematic external perspective view showing the firstembodiment of a signature verification system in accordance with theinvention. FIG. 5 is a schematic vertical sectional view showing thesignature input apparatus used in the first embodiment. Signature inputapparatus 1, as apparent from FIG. 5, is composed of a liquid crystalsheet 2 and a coordinate input unit 3. Liquid crystal sheet 2 is appliedto coordinate input unit 3 with a sticky material so that liquid crystalsheet 2 can repeatedly adhere thereto and separate there from. Liquidcrystal sheet 2 is fabricated as follows: Aluminum is evaporated on abase 35 made up of polyethylene terephthalate film. This aluminum film34 forms a conductive layer 34. Formed on conductive layer 34 is aliquid crystal dispersed polymer layer 33 in which liquid crystaldroplet 31 are dispersed in a polymer matrix 32. Finally, a transparent,surface protecting layer 30 is laminated on liquid crystal dispersedpolymer layer 33. In this way, liquid crystal sheet 2 is completed.Here, conductive layer 34 is electrically connected to the conductivematerial to which an operation start button 21 in FIG. 4 is applied.This operation start button 21 works as a contact electrode.

Coordinate input unit 3 is fabricated from a base 42 also serving as theinsulating member, a Y-axis coordinate resistance sheet 41 formedthereon, a pressure-sensitive sheet 40, an electrode sheet 39, apressure-sensitive sheet 38, an X-axis coordinate resistance sheet 37and a flexible sheet 36 made up of an insulative material forprotection, all being laminated successively in this order. Further,Y-axis coordinate resistance sheet 41 and X-axis coordinate resistancesheet 37 are connected to a detecting circuit 43 for detecting thehandwriting coordinate information of a signature written by dedicatedpen 5.

FIG. 6 is a conceptual diagram showing the coordinate detecting portionof a coordinate input unit 3 shown in FIG. 5. A voltage V is applied toelectrode sheet 39, which is sandwiched between pressure-sensitivesheets 38 and 40. These sheets have high resistance if they receive nopressure and reduce to a markedly low level, in their resistance, acrosstheir thickness if a pressure exceeding a predetermined level isapplied. Provided in contact with the opposite sides of sensitive sheet38 and 40, to electrode sheet 39, are X-axis coordinate resistance sheet37 and Y-axis coordinate resistance sheet 41, each having uniformresistance. Current extracting electrodes 37' and 41' are provided onboth ends of X-axis coordinate resistance sheet 37 and Y-axis resistancesheet 41, respectively. Each of these current extracting electrodes 37'and 41' are connected to detecting circuit 43, so that each current canbe measured.

In this arrangement, when a writing pressure exceeding a predeterminedlevel is applied to an arbitrary point P on display area 7 of liquidcrystal sheet 2, using dedicated pen 5, the pressure is transferred toeach of pressure-sensitive sheets 38 and 40, whereby the resistancevalues of pressure-sensitive sheets 38 and 40 across their thickness atthe point P change to a very low level. As a result, a voltage V isapplied to at the point P on both X-axis coordinate resistance sheet 37and Y-axis coordinate resistance sheet 41 through each ofpressure-sensitive sheets 38 and 40. Here, considering the case ofX-axis coordinate resistance sheet 37 only, currents I_(X1) and I_(X2)flowing from the point P to current extracting electrodes 37' atrespective ends are proportional to the reciprocals of resistance valuesR_(X1) and R_(X2) from the point P to current extracting electrodes 37'at respective ends. The ratio of R_(X1) and R_(X2) is proportional tothe ratio of the distances from the point P in the X-axis direction.Therefore, it is possible to determine the X-coordinate of the point Pby measuring the ratio of currents I_(X1) and I_(X2). Similarly, it ispossible to determine the Y-coordinate of the point P by measuring theratio of I_(Y1) and I_(Y2).

Next, description will be made of dedicated pen 5 used in thisembodiment. FIG. 7 is a schematic vertical sectional view showing theinner structure of dedicated pen 5 used in signature input apparatus 1of this embodiment. As shown in FIG. 7, dedicated pen 5 incorporates awriting switch 22, a power source 48 and a voltage generator 49 forapplying static charge to liquid crystal sheet 2. Attached at both endsof dedicated pen 5 are a pair of writing elements 44 and 47 for thinlines and for thick lines, which are of a conductive material andtransmit the writing pressure to pressure-sensitive sheet 38 and 40 ofcoordinate input unit 3 so as to point the coordinates of thehandwriting of a signature whilst applying static charge to liquidcrystal sheet 2. Thus, it is possible to deal with the functions ofsignature input apparatus 1 (writing with thick lines and writing withthin lines). These, thin-line writing element 44 and thick-line writingelement 47, are electrically connected, as shown in FIG. 7, to voltagegenerator 49 via writing switch 22. A barrel cylinder 45 of dedicatedpen 5 is made from an insulative material. An outer sleeve 46 made froma conductive material is provided on the outer peripheral surface ofbarrel cylinder 45. Here, outer sleeve 46 is electrically connected tothe negative output from voltage generator 49.

Now, referring mainly to FIG. 4, description will be made about theoperations of the signature verification system comprising signatureinput apparatus 1 having thus fabricated liquid crystal sheet 2 andcoordinate input unit 3, and signature verifying apparatus 6. First, apower switch 18 of signature input apparatus 1 is turned on, and powersource 48 of dedicated pen 5 whilst it is gripped by one hand, is turnedon by pressing writing switch 22. FIG. 7 mentioned above shows the statein which power source 48 is turned on. As power source 48 is turned onin this way, writing elements 44 and 47 and one of the output terminalsfor writing from voltage generator 49 are electrically connected.

Next, after writing button 19 is pressed so as to select the writingfunction of signature input apparatus 1, an operation start button 21 ofsignature input apparatus 1 is pressed by the finger of the other handwhilst writing switch 22 of dedicated pen 5 is being pressed. Thus, thecontact electrode which covers operation start button 21 comes incontact with a part of the person's body, the contact electrode ofoperation start button 21 and outer sleeve 46 of dedicated pen 5 areelectrically connected via the person's body. Further, since conductivelayer 34 of liquid crystal sheet 2 is connected to the contact electrodeof operation start button 21 as stated above, conductive layer 34 isresultantly connected electrically to outer sleeve 46 of dedicated pen5. At this time, an applied voltage for writing is output to writingelements 44 and 47 from voltage generator 49.

Then, whilst operation start button 21 is pressed by the finger of theother hand, the signature is made by pressing thin-line writing element44 or thick-line writing element 47 of dedicated pen 5 onto the displayarea 7 of liquid crystal sheet 2. At this time, static charge is appliedto the written portion on display area 7 of liquid crystal sheet 2, andliquid crystal droplet 31 in liquid crystal dispersed polymer layer 33are aligned by the electrostatic field. Consequently, handwriting 23 ofthe signature appears as a liquid crystal representation, on displayarea 7 of liquid crystal sheet 2. At the same time, the handwritingcoordinate information and writing pressure data of the signaturewritten by dedicated pen 5 are detected by coordinate input unit 3 of apressure-sensitive resistance type.

The handwriting of a signature written on display area 7 of liquidcrystal sheet 2 by the above method, disappears by itself after apredetermined period of time because, after the liquid crystal display,the static charge applied to the handwriting portion moves at the topand bottom of liquid crystal dispersed polymer layer 33 and surfaceprotecting layer 30 in liquid crystal sheet 2 and is neutralized withthe passage of time.

Conductive writing elements 44 and 47 of dedicated pen 5 may be formedof an elastic material which is deformable by external force. Thisconfiguration enables writing elements 44 and 47 to be in contact withliquid crystal sheet 2 in a varying area in accordance with the writingpressure. That is, with the writing pressure being low, the contact areais smaller, whereas with the writing pressure being high, the contactarea is larger. Thus, it is possible to easily change the width of thehandwriting of a signature in accordance with the writing pressure.

The handwriting coordinate information and writing pressure data of asignature detected by coordinate input unit 3 are transferred tocomputer 14 incorporating communications software, verification softwareand registration memories, where signature registration or signatureverification is implemented. Computer 14 is connected to a variety ofnetworks 16 via a dedicated or multi-purpose communication line, and theresult of the signature verification is used to implement door unlockingoperation 17. As stated above, computer 14 has a switching mechanismwhich determines whether the signature verification system of thisembodiment is used as an isolated system for performing only doorunlocking operation 17, or is only used for connection to network 16, oris used for both. Further, computer 14 informs instruction of the startand end of signature input and re-input etc. and verification result byway of speaker 13.

The Second Embodiment

FIG. 8 is a block diagram showing the second embodiment of a signatureverification system in accordance with the invention. FIG. 9 is a blockdiagram showing the interior of the signature input apparatus shown inFIG. 8. FIG. 10 is a schematic external perspective view showing thesecond embodiment of a signature verification system in accordance withthe invention. Here, the same components as in the signatureverification system of the above first embodiment are designated withthe identical reference numerals used in the first embodiment and thedescription thereof is omitted.

The difference from the signature verification system of the firstembodiment, is that as shown in FIGS. 8 through 10, the signature inputportion composed of a liquid crystal sheet 2 and a coordinate input unit3 and a computer 14 functioning as signature verification apparatus 6are integrated into a signature input apparatus 51. Other configurationis the same as that of the signature verification system of the firstembodiment and the signing operation etc. are also the same.

The Third Embodiment

FIG. 11 is a block diagram showing the third embodiment of a signatureverification system in accordance with the invention. FIG. 12 is a blockdiagram showing the interior of the signature input apparatus shown inFIG. 11. Here, the same components as in the signature verificationsystems of the first and second embodiments are designated with theidentical reference numerals used in the first and second embodimentsand the description thereof is omitted.

As shown in FIGS. 11 and 12, a coordinate input unit 56 of a signatureinput apparatus 55 used in the signature verification system of thisembodiment is of an electromagnetic induction type. Therefore, signatureinput apparatus 55 incorporates a power source 57 for a liquid crystalsheet as well as using a dedicated pen 58 having the function ofapplying static charge onto liquid crystal sheet 2 and having a specialinner structure (the inner structure will be detailed later). In thiscoordinate input unit 56 of an electromagnetic induction type, thehandwriting of a signature is detected by not only detecting the X-axisand Y-axis coordinate data and writing pressure data from the in-contactwritten part by dedicated pen 58, onto liquid crystal sheet 2 within acoordinate input area 65 of this coordinate input unit 56, but also bydetecting the X-axis and Y-axis coordinate data of the locus ofdedicated pen 58 floating away from the liquid crystal sheet, within acertain range of height, over and within coordinate input area 65, bymeans of an X-axis driver circuit 66, Y-axis driver circuit 67, andtransmission/reception circuit 68 and CPU 69 connected thereto.

The X-axis and Y-axis coordinate data (including the floating state) andwriting pressure data of the handwriting of the signature thus detectedby coordinate input unit 56 are transferred to signature verifyingapparatus 6, where they are used for signature registration andsignature verification. In this embodiment, as signature verifyingapparatus 6, a personal computer (to be referred to as `PC` hereinbelow)59 having verification software (coordinate input software) andcommunications software installed therein. This PC 59 is connected to adisplay 60, keyboard 61, mouse 62 and communication unit 63.Communication unit 63 is further connected to a variety of networks 64via a dedicated or multi-purpose communication line.

FIG. 13 is a schematic external perspective view showing the thirdembodiment of a signature verification system in accordance with theinvention. FIG. 14 is a schematic vertical sectional view showing thesignature input apparatus used in the third embodiment. Guidance forinstruction of the start of input of a signature, the end of input ofthe signature, and re-input etc. as well as the verification result etc.is displayed on display 60. Handwriting 23 of a signature written bydedicated pen 58 onto a display area 7 of liquid crystal sheet 2 isdisplayed as a liquid crystal representation, at the same time, itshandwriting 53 is displayed on display 60. Handwriting 23 of a signaturethus obtained on liquid crystal sheet 2 will disappear by itself after apredetermined period of time. Handwriting 53 of the signature imaged ondisplay 60 is deleted by a command operation from keyboard 61, or byinstructing the delete command which is outside the handwriting displayarea on this display 60, using coordinate input unit 56 or mouse 60 etc.Alternatively, the handwriting on the display may be adapted to beautomatically deleted after a lapse of a predetermined period of time,or to be replaced by a display of the verification result of the inputsignature or by a display of the next operation instructions and thelike.

Signature input apparatus 55, as apparent from FIG. 14, is configuredsuch that, liquid crystal sheet 2 is adhered onto coordinate input unit56 with a sticky material, so as to allow the sheet to be repeatedlyadhere thereto and separate therefrom. Coordinate input unit 56 is of anelectromagnetic induction type as stated above, and is fabricated bysuccessively laminating a Y-axis directional coil layer 73, aninsulating layer 72, an X-axis directional coil layer 71 and aprotecting film layer 70, on a base 74, in this order.

Signature input apparatus 55 incorporates power source 57 for a liquidcrystal sheet for applying static charge to liquid crystal sheet 2 asstated above and one of the output terminals from power source 57 for aliquid crystal sheet is electrically connected to a conductive layer 34of liquid crystal sheet 2. Further, the other output terminal from powersource 57 for a liquid crystal sheet is electrically connected to awriting contact electrode 76.

FIG. 15 is a conceptual diagram showing the coordinate detecting portionof the coordinate input unit shown in FIG. 14. In X-axis direction coillayer 71, a large number of X-axis loop coils (not shown) are arrangedin the X-axis direction, overlapping one over another at intervals of acertain distance. Similarly, in Y-axis direction coil layer 73, a largenumber of Y-axis loop coils (not shown) are arranged in the Y-axisdirection, overlapping one over another at intervals of a certaindistance. All the X-axis loop coils or all the Y-axis loop coils aresuccessively switched to be connected to a transmission/receptioncircuit for X-axis loop coils or Y-axis loop coils, at intervals of apredetermined time, by a scanning circuit of an electronic switch (notshown). Transmission/reception circuit 68 in FIG. 12 is composed of atransmission circuit for imparting electromagnetic energy in the form ofa.c. magnetic flux to dedicated pen 58 and a reception circuit forreceiving the response in a form of a.c. magnetic flux ofelectromagnetic energy accumulated in dedicated pen 58, and performs thetransmission and reception alternately. Further, the output from thereception circuit is connected to a calculating circuit (not shown) forcalculating the coordinates.

Here, when an operation of a certain X-axis loop coil, which is directlybelow dedicated pen 58 (the inner structure will be detailed later)placed at an arbitrary point P on liquid crystal sheet 2, is observed,the X-axis loop coil performs a radiation of a.c. magnetic flux forimparting electromagnetic energy to dedicated pen 58. Dedicated pen 58receives this a.c. magnetic flux, using its coil, and accumulates theelectromagnetic energy with an LC resonant circuit in dedicated pen 58.After the a.c. magnetic flux from the X-axis loop coil has been cut off,the electromagnetic energy accumulated in the LC resonant circuit isreleased through the coil of dedicated pen 58, to perform a radiation ofa.c. magnetic flux over a predetermined period of time to coordinateinput unit 56. The X-axis loop coil which has finished its radiation andis in the reception state, receives the a.c. magnetic flux fromdedicated pen 58, and sends the signal to the calculating circuit (notshown) via the receiving circuit. The calculating circuit makes acomparison between the received signal from the X-axis loop coil and thereceived signal from X-axis loop coils proximal thereto, thusdetermining the X-axis coordinate. Similarly, the same operations areperformed for the Y-axis loop coils to determine the Y-axis coordinate.

Next, description will be made of dedicated pen 58 used in thisembodiment. FIG. 16 is a schematic vertical sectional view showing theinner structure of dedicated pen 58 used in signature input apparatus 55of this embodiment. As shown in FIG. 16, dedicated pen 58 has a innersleeve 86 consisting of an insulating material and a barrel cylinder 80consisting of a conductive material which covers this inner sleeve 86.Arranged inside inner sleeve 86 are an LC resonant circuit 81, a writingpressure detector 82, a core member 83 of an insulating material, awriting element 85 of a conductive material, attached at the front endof a coil portion 84 and core member 83. Here, writing element 85 iselectrically connected to barrel cylinder 80 but not fixed to barrelcylinder 80. This is because it becomes impossible to detect writingpressure through writing pressure detector 82 if it is fixed. LCresonant circuit 81 and coil portion 84 function as stated above. Barrelcylinder 80 is made up of a conductive material which will not disturbthe transmission and reception in the form of a.c. magnetic flux asstated above between each of the loop coils in the coordinate input unitand the coil of the dedicated pen 58. It is also possible to use abarrel cylinder 80 made up of a non-conductive material and provide anopening having a size which will not disturb the propagation of a. c.magnetic flux in the direction toward the tip of the writing element.

Conductive writing element 85 of dedicated pen 58 may be formed of anelastic material which is deformable by external force. Thisconfiguration enables writing element 85 to be in contact with liquidcrystal sheet 2 in a varying area in accordance with the writingpressure. That is, with the writing pressure being low, the contact areais smaller, whereas with the writing pressure being high, the contactarea is larger. Thus, it is possible to easily change the width of thehandwriting of a signature in accordance with the writing pressure.

Now, referring mainly to FIG. 13, description will be made about theoperations of the signature verification system thus configured. First,a power source switch 75 of liquid crystal sheet power source 57 and apower switch 54 of PC 59 are turned on. Power to signature inputapparatus 55 is supplied externally though it is not illustrated. Withdedicated pen 58 being gripped by one hand, writing contact electrode 76is touched by a finger of the other hand. This electrically connectsliquid crystal sheet power source 57 with barrel cylinder 80 ofdedicated pen 58 through the person's body, and consequently, a voltageto be applied liquid crystal sheet 2 is output at writing element 85provided at the tip of dedicated pen 58.

When a signature is made by bringing dedicated pen 58 into contact withdisplay area 7 of liquid crystal sheet 2, static charge is applied tothe written portion on liquid crystal sheet 2 so that liquid crystal 31in liquid crystal dispersed polymer layer 33 are aligned by theelectrostatic field. Consequently, handwriting 23 of the signatureappears as a liquid crystal representation, on display area 7 of liquidcrystal sheet 2. At the same time, the handwriting coordinateinformation (including that from when dedicated pen 58 is floating) andwriting pressure data of the signature written by dedicated pen 58 aredetected by coordinate input unit 56 of an electromagnetic inductiontype, based on the aforementioned principle of coordinate detection.Then, the data thus detected in coordinate input unit 56 is sent to PC59, where it is converted into a coordinate position on display 60 sothat handwriting 53 identical with handwriting 23 of the signatureappearing on display area 7 is displayed on display 60.

Handwriting 23 of a signature written on display area 7 of liquidcrystal sheet 2 by the above method, will disappear by itself after apredetermined period of time because, after the liquid crystal display,the static charge applied to the handwriting portion moves at the topand bottom of liquid crystal dispersed polymer layer 33 and surfaceprotecting layer 30 in liquid crystal sheet 2 and is neutralized withthe passage of time.

The handwriting coordinate information and writing pressure data of asignature detected by coordinate input unit 56 are transferred to PC 59incorporating communications software and verification software, wheresignature registration or signature verification is implemented. PC 59is connected to communication device 63, as stated above, and thiscommunication device 63 is further connected to a variety of networks 64via a dedicated or multi-purpose communication line. In accordance withthe result of the signature verification, the PC 59 is connected tocommunication device 63 and network 64 via a communication line. In thisembodiment, the hard disc in PC 59 plays the role of the registrationmemories, which are incorporated in the computers of the first andsecond embodiment. PC 59 gives instruction of the start and end of inputof a signature, re-input etc. as well as the verification result, bydisplaying them on display 60. Although control of signatureverification is performed by signature input apparatus 55 in accordancewith the above description, it is also possible to be controlled throughkeyboard 61 or mouse 62 which are connected to PC 59.

In the first and second embodiments, coordinate input unit 3 of apressure-sensitive resistance type is used whereas coordinate input unit56 of an electromagnetic induction type is used in the third embodiment.However, these can be replaced as stated above, by a coordinate inputunit of a magnetostrictive plate type, for example. FIG. 17 is aconceptual diagram showing the configuration of a coordinate input unitof a magnetostrictive plate type. As shown in FIG. 17, a coordinateinput unit 90 of a magnetostrictive plate type comprises: an X-axisoscillation exciting coil 92 and a Y-axis oscillation exciting coil 93which are wound along counter sides of a magnetostrictive plate 91 forgenerating magnetostrictive vibrations in the directions of the X-axisand the Y-axis of magnetostrictive plate 91; driver circuits 94 and 95which are connected to respective oscillation-exciting coils 92 and 93for driving respective oscillation-exciting coils 92 and 93; a countercircuit 96 for counting time; a triggering circuit 97 for triggeringtiming of each of circuits 94, 95 and 96; and a calculating circuit 98for calculating the distance. Designated at 99 is a detecting pen forconverting the change in magnetic flux due to magnetostriction vibrationinto an electrical signal.

Next, the detecting operation of coordinate data by the coordinate inputunit of a magnetostrictive plate type will be described. First, when apulse current is applied to X-axis oscillation exciting coil 92 ofmagnetostrictive plate 91, the oscillation-exciting magnetic fieldgenerates a magnetostriction vibration, so that a magnetostriction waveW_(X) propagates at a speed V, perpendicularly to X-axis oscillationexciting coil 92, toward the other side of magnetostrictive plate 91.This magnetostriction wave W_(X) reaches an arbitrary point P_(X) onmagnetostrictive plate 91 where detecting pen 99 is placed, and thereinthe wave is electrically detected. Here, when the distance fromdetecting pen 99 to X-axis oscillation exciting coil 92 is L, and thetime taken by magnetostriction wave W_(X) from the time the pulsecurrent is applied to oscillation exciting coil 92 to the time themagnetostriction wave W_(X) reaches detecting pen 99 is T_(X), arelation L_(X) =V·T_(X) holds. Accordingly, provided that the case wherethe propagating speed V is always constant, it is possible to calculatethe distance L_(X) by measuring the arrival time T_(X) so as todetermine a coordinate point P_(X) on the X-axis. A similar operationcan be performed for the Y-axis, so that is possible to determine acoordinate point P_(Y) on the Y-axis. Thus, it is possible to detectcoordinate values P_(X) and P_(Y) of the position of detecting pen 99,which are placed at an arbitrary point P on magnetostrictive plate 91.

EXAMPLES

Next, the spontaneous disappearance of the handwriting of a signaturewritten on the liquid crystal sheet will be described in detail withreference to examples and comparative examples.

Example 1

Liquid crystal sheet 2 of the invention was fabricated by the followingprocedures. That is, a deposited aluminum layer of #50 Metalmy (aproduct of TOYO METALLIZING CO., LTD.: an aluminum deposited film ofwhich base 35 is of a polyethylene terephthalate film) was used asconductive layer 34. A solution having the following composition wasapplied to this conductive layer 34 and dried forming a liquid crystalpolymer layer 33, which is composed of liquid crystal 31 and polymermatrix 32, so that the dry film thickness was 6 μm.

S-LEC BX-L (a product of SEKISUI CHEMICAL CO., LTD.:

polyvinyl butyral) 10% MEK/toluene mixture solution 4.0 g

E44 (a product of MERCK CORPORATION: nematic liquid crystal) 0.4 g

An aqueous solution of Joncryl J-352 (a product of Johnson PolymerCorporation: acrylic emulsion) was applied as a surface protecting layer30 onto the above liquid crystal dispersed polymer layer 33 and dried sothat the dry film thickness was 4 μm. Thus, liquid crystal sheet 2 wasprepared.

For the above liquid crystal dispersed polymer layer 33 and surfaceprotecting layer 30 which were humidity controlled at 90% RH at atemperature of 20° C., the volume resistivity was measured using DigitalUltra-High Resistance/Micro Current Meter (a product of ADVANTESTCORPORATION: R8340A) and Sample Box for Ultra High ResistanceMeasurement (a product of ADVANTEST CORPORATION: TR42). The results wereas follows:

    ______________________________________                                        Liquid crystal dispersed polymer layer                                                             2.0 × 10.sup.14 Ω · cm              Surface protecting layer                                                                           6.2 × 10.sup.14 Ω · cm              ______________________________________                                    

When, a d.c. voltage of 200 V was applied to the liquid crystal sheet 2thus prepared, using dedicated pen 5, liquid crystal 31 corresponding tothe portion of handwriting 23 in liquid crystal dispersed polymer layer33 was aligned by the electric field, so that handwriting 23 could berecognized. Then, handwriting 23 disappeared by itself after 10 secondhad elapsed after writing because the static charge applied to theportion of handwriting 23 moved at the top and bottom of liquid crystaldispersed polymer layer 33 and surface protecting layer 30 and wasneutralized or nullified with the passage of time.

Example 2

A liquid crystal sheet 2 was prepared in a similar manner to example 1except in that a solution having the following composition was appliedand dried forming a liquid crystal polymer layer 33 so that the dry filmthickness was 7 μm.

S-LEC KS-1 (a product of SEKISUI CHEMICAL CO., LTD.: polyvinyl acetal)10% ethyl acetate solution 4.0 g

E44 (a product of MERCK CORPORATION: nematic liquid crystal) 0.4 g

The volume resistivity of the thus obtained liquid crystal dispersedpolymer layer 33 was measured in a similar manner to example 1.

Liquid crystal dispersed polymer layer

    1.2×10.sup.15 Ω.cm

When, a d.c. voltage of 200 V was applied to the liquid crystal sheet 2thus prepared, using dedicated pen 5, liquid crystal 31 corresponding tothe portion of handwriting 23 in liquid crystal dispersed polymer layer33 was aligned by the electric field, so that handwriting 23 could berecognized. Then, handwriting 23 disappeared by itself after about 1 to2 minutes had elapsed after writing because the static charge applied tothe portion of handwriting 23 moved at the top and bottom of liquidcrystal dispersed polymer layer 33 and surface protecting layer 30 andwas neutralized or nullified with the passage of time.

Comparative example 1

A solution mixture having the following composition was prepared by anultrasonic dispersing device, to produce an emulsified dispersedsolution in which liquid crystal 31 was micro-dispersed in a polyvinylalcohol aqueous solution. This emulsified dispersed solution was appliedand dried so that the dry film thickness was 9 μm. Except for theseconditions, liquid crystal sheet 2 was prepared in a similar manner toexample 1.

GOHSENOL GH-17 (a product of The Nippon Synthetic Chemical Industry Co.,Ltd.: polyvinyl alcohol) 10% aqueous solution 4.0 g

E44 (a product of MERCK CORPORATION: nematic liquid crystal) 0.4 g

The volume resistivity of the thus obtained liquid crystal dispersedpolymer layer 33 was measured in a similar manner to example 1.

Liquid crystal dispersed polymer layer

    1.0×10.sup.12 Ω.cm

When, a d.c. voltage of 200 V was applied to the liquid crystal sheet 2thus prepared, using dedicated pen 5, the static charge applied to thehandwriting portion moved and was neutralized quickly, without beingsuspended at the top and bottom of liquid crystal dispersed polymerlayer 33, since the volume resistivity of liquid crystal polymer layer33 was too low. Thus, it was impossible to recognize the handwriting.

Comparative example 2

A liquid crystal sheet 2 was prepared in a similar manner to example 1except in that a solution having the following composition was appliedand dried forming a liquid crystal polymer layer 33 so that the dry filmthickness was 7 μm.

S-LEC KS-1 (a product of SEKISUI CHEMICAL CO., LTD.: polyvinyl acetal)10% ethyl acetate solution 4.2 g

TAKENATE D110N(a product of Takeda Chemical Industries, Ltd.:polyisocyanate) 0.56 g

E44 (a product of MERCK CORPORATION: nematic liquid crystal) 0.36 g

The volume resistivity of the thus obtained liquid crystal dispersedpolymer layer 33 was measured in a similar manner to example 1.

Liquid crystal dispersed polymer layer

    1.2×10.sup.17 Ω.cm

When, a d.c. voltage of 200 V was applied to the liquid crystal sheet 2thus prepared, using dedicated pen 5, liquid crystal 31 corresponding tothe portion of handwriting 23 in liquid crystal dispersed polymer layer33 was aligned by the electric field, so that handwriting 23 could berecognized. However, since the volume resistivity of liquid crystaldispersed polymer layer 33 was too high, the static charge applied tothe portion of handwriting 23 did not move at the top and bottom ofliquid crystal dispersed polymer layer 33 and hence was not neutralizedafter a certain period of time. Therefore, handwriting 23 did notdisappear completely even after more than 10 minutes had elapsed afterwriting.

Comparative example 3

A liquid crystal sheet 2 was prepared in a similar manner to example 1except in that CROSLENE SA-54 (a product of Takeda ChemicalIndustries,Ltd.: styrene-butadiene rubber emulsion) was applied anddried on conductive layer 34 and liquid crystal dispersed polymer layer33 of the same type as in example 1, forming a surface protecting layer30, so that the dry film thickness was 6 μm.

The volume resistivity of surface protecting layer 30 was measured in asimilar manner to example 1.

Surface surface protecting layer

    4.0×10.sup.8 Ω.cm

When, a d.c. voltage of 200 V was applied to the liquid crystal sheet 2thus prepared, using dedicated pen 5, the handwriting spread as if itwere blotting and could not be recognized because the volume resistivityof surface protecting layer 30 was too low and hence the static chargeapplied to the handwriting portion spread quickly over the surface ofthe surface protecting layer.

Comparative example 4

A liquid crystal sheet 2 was prepared in a similar manner to example 1except in that Tetoron film F (a product of TEIJIN CO., LTD.:polyethylene terephthalate film) of 9 μm thick, was laminated as asurface protecting layer 30, on conductive layer 34 and liquid crystaldispersed polymer layer 33 of the same type as in example 1, using asticky material.

The volume resistivity of surface protecting layer 30 was measured in asimilar manner to example 1.

Surface protecting layer

    3.1×10.sup.17 Ω.cm

When, a d.c. voltage of 200 V was applied to the liquid crystal sheet 2thus prepared, using dedicated pen 5, liquid crystal 31 corresponding tothe portion of handwriting 23 in liquid crystal dispersed polymer layer33 was aligned by the electric field, so that handwriting 23 could berecognized. Though handwriting 23 disappeared by itself after 10 secondhad elapsed after writing, the static charge was suspended on the topand bottom of surface protecting layer 30 because the volume resistivityof surface protecting layer 30 was too high, and hence handwriting couldnot be obtained when another writing step was performed over thehandwriting which had disappeared.

INDUSTRIAL APPLICABILITY

As has been described in detail, in accordance with the signature inputapparatus and signature verification system of the invention, when asignature is written on the liquid crystal sheet attached on the surfaceof the coordinate input unit, by a coordinate pointer having thefunction of applying static charge, smooth handwriting appears as itsliquid crystal representation, on the liquid crystal sheet screen.Therefore, a signature can be written easily, and the precision of thesignature can be improved, so that it is possible to improve theaccuracy of signature registration and signature verification.

Further, since the handwriting of a signature written on the liquidcrystal sheet disappears by itself without holding up the signer after apredetermined period of time, there is no concern that the handwritingwill be viewed by others, thus improving the security. Moreover, sincethe liquid crystal sheet has a simple structure, the cost can also belowered also it is possible to easily attach the liquid crystal sheeton, and detach it from, the surface of a coordinate input unit on themarket.

What is claimed is:
 1. A signature input apparatus comprising:a liquidcrystal sheet having a conductive layer and a liquid crystal dispersedpolymer layer in which a liquid crystal is dispersed in a polymermatrix; a coordinate pointer for applying static charge onto the liquidcrystal sheet causing the handwriting of a signature to appear as aliquid crystal representation; and a coordinate input unit for detectinghandwriting coordinate information of the signature written on theliquid crystal sheet, wherein the static charge applied to the polymermatrix neutralizes by itself over a period of time, causing thehandwriting of the signature written on the liquid crystal sheet todisappear solely by itself within a period of time of two minutes orless and commensurate with prevention of unauthorized observation and/orcoping of the written signature.
 2. The signature input apparatusaccording to claim 1, wherein the liquid crystal sheet further includesa transparent, surface protecting layer, the conductive layer, theliquid crystal dispersed polymer layer and the surface protecting layerbeing laminated successively in that order.
 3. The signature inputapparatus according to claim 1 or claim 2, wherein the liquid crystalsheet is removably attached to the surface of the coordinate input unit.4. The signature input apparatus according to claim 1 or claim 2,wherein the polymer matrix comprises a cross-linking polymer obtained byreacting di- or poly-isocyanate with polyvinyl acetal resin.
 5. Thesignature input apparatus according to claim 1 or claim 2, wherein theliquid crystal is a nematic liquid crystal having a positive anisotropicdielectric constant, and the differential index of birefringence is 0.2or more.
 6. The signature input apparatus according to claim 1, whereinthe volume resistivity of the liquid crystal dispersed polymer layer isequal to or greater than 10¹³ Ω.cm and lower than 10¹⁶ Ω.cm at atemperature of 20° C. at a relative humidity of 90%.
 7. The signatureinput apparatus according to claim 2, wherein the volume resistivity ofthe liquid crystal dispersed polymer layer is equal to or greater than10¹³ Ω.cm and lower than 10¹⁶ Ω.cm at a temperature of 20° C. at arelative humidity of 90%, and the volume resistivity of the surfaceprotecting layer is equal to or greater than 10⁹ Ω.cm and lower than10¹⁶ Ω.cm at a temperature of 20° C. at a relative humidity of 90%.
 8. Asignature verification system comprising:(A) a signature input apparatuscomprising: a liquid crystal sheet having a conductive layer and aliquid crystal dispersed polymer layer in which a liquid crystal isdispersed in a polymer matrix, a coordinate pointer for applying staticcharge onto the liquid crystal sheet causing the handwriting of asignature to appear as a liquid crystal representation, and a coordinateinput unit for detecting the handwriting coordinate information of thesignature, wherein the static charge applied to the polymer matrixneutralizes by itself over a period of time, causing the handwriting ofthe signature written on the liquid crystal sheet to disappear solely byitself within a period of time of two minutes or less and commensuratewith prevention of unauthorized observation and/or copying of thewritten signature; and (B) a signature verifying apparatus for readingthe handwriting coordinate information of a signature output from thecoordinate input unit and verifies the handwriting coordinateinformation with the handwriting coordinate information of signaturesregistered beforehand.
 9. The signature verification system according toclaim 8, wherein the liquid crystal sheet further includes atransparent, surface protecting layer, the conductive layer, the liquidcrystal dispersed polymer layer and the surface protecting layer beinglaminated successively in that order.
 10. The signature verificationsystem according to claim 8 or claim 9, wherein the liquid crystal sheetis removably attached to the surface of the coordinate input unit. 11.The signature verification system according to claim 8 or claim 9,wherein the polymer matrix is composed of a cross-linking polymerobtained by reacting di- or poly-isocyanate with polyvinyl acetal resin.12. The signature verification system according to claim 8 or claim 9,wherein the liquid crystal is a nematic liquid crystal having a positiveanisotropic dielectric constant, and the differential index ofbirefringence is 0.2 or more.
 13. The signature verification systemaccording to claim 8, wherein the volume resistivity of the liquidcrystal dispersed polymer layer is equal to or greater than 10¹³ Ω.cmand lower than 10¹⁶ Ω.cm at a temperature of 20° C. at a relativehumidity of 90%.
 14. The signature verification system according toclaim 9, wherein the volume resistivity of the liquid crystal dispersedpolymer layer is equal to or greater than 10¹³ Ω.cm and lower than 10¹⁶Ω.cm at a temperature of 20° C. at a relative humidity of 90%, and thevolume resistivity of the surface protecting layer is equal to orgreater than 10⁹ Ω.cm and lower than 10¹⁶ Ω.cm at a temperature of 20°C. at a relative humidity of 90%.
 15. The signature input apparatusaccording to either of claims 1 or 8, wherein the signature written onthe liquid crystal sheet disappears by charge movement within the liquidcrystal sheet.